Method and apparatus for subterranean heating



May 4, 1965 R. F. KRUEGER 3,181,613

METHOD AND APPARATUS FOR SUBTERRANEAN HEATING Original Filed July 20, 1959 fz- Z United States Patent O 3,181,613 METHD AND APPARATUS FR SUBTEANEAN ATENG Roland F. Krueger, Anaheim, Calif., assigner to Union Gil Company of California, Los Angeles, Calif., a cor-1 poration of California Original application July Ztl, 1959, Ser. No. 828,106, new Patent No. 3,113,623, dated Dec. 10, 1963. Divided and this application Apr. 23, 1953, Ser. No. 274,992 8 Claims. (Cl. Mtn-38) This invention relates to a novel method and apparatus for uniformly heating an elongated region of mineral deposits located beneath the earths surface, and more particularly concerns a method and apparatus for the thermal recovery of hydrocarbon values from subterranean deposits comprising the same.

A number of processes have been proposed employing heat to facilitate the recovery of hydrocarbon values from subterranean deposits such as bituminous sands, oil shale, bituminous and sub-bituminous coals, oil-soaked diatomite, heavy petroleum deposits, and the like. In most of these processes, at least part of the heat is supplied from a burner positioned in a bore hole drilled into the mineral deposit. For example, according to one process which has been applied to the treatment of tar sand deposits, a plurality of relatively closely-spaced holes are drilled into the deposit, and heat is generated in a selected number of these holes by combustion of gas or other fuel in a suitably positioned burner device. The surrounding sand is thereby heated and the volatile pertoleum fractions are driven towards a production bore hole from which they are recovered. The heavier ends which fail to volatilize are pyrolyzed by continued heating. As previously practiced, a single burner has been positioned at the base of the formation or at a point along the combustion tube. This technique results in localized heating, which is useful with shallow formations but not readily applicable where the formation is vertically extended.

The conventional flame obtained with commonly ernployed open end burner tubes is of a conical shape and extends only a short distance from the burner tip. The shape ofthis flame is shown in photographs and sketches in the ,following publications of the National Advisory Committee for Aeronautics: NACA Research Memorandum, E54F29, August 1954; and NACA Technical Note No. 1707, September 1948. This typical short conical flame causes localized heating of oil sands because the majority of the heat release occurs in the flame zone which is usually much shorter than the thickness of the oil bearing strata. Prior art devices have been unable to conveniently extend the flame zone for a distance greater than that normally obtainable with an open end burner, thus being unable to secure a substantially uniform heat release through the depth of the oil bearing interval.

Attempts to use this localized heating to transmit heat to an elongated zone within subterranean deposits have employed flow reversal methods, alone, or with packed annular zones of coarse inert material around the burner zone, or with an annular fluidized bed of finely divided inert solids. In the flow reversal method of heating, a combustion tube is concentrically placed within the bore hole and extended nearly to the base of the hole. Combustible fuel gases and air are mixed in the tube and ignited at a selected point. The llame front is prevented from rising up the combustion tube by flame arresting .means positioned upstream from the llame. The combustion gases pass downwardly from the burner tube to the base of ythe hole where they reverse their direction and tlow upwardly through the annulus between the combustion tube and bore casing. It has been found that a4 high ltemperature zone within the mineral deposit exists immediately adjacent the burner flame, and that the temperalhll Patented May 4, 1965 ICC ture of the mineral deposit at points vertically removed from this high temperature zone are substantially less. This type of operation is no-t entirely satisfactory because the heat is not efficiently distributed and the localized high temperature zone causes thermal failure of the burner tube. While use of a fluidized bed of solids within the annulus between the burner and casing improves heat transfer to the mineral deposit, it does not completely eliminate the uneven heating along the bore hole and is disadvantageous in that it causes a high erosion rate of the metal surfaces.

It is accordingly an object of this invention to provide an improved method for subterranean heating.

It is a further object of the invention to provide a unique burner which achieves uniform heating over an extended length and which has a long service life.

It is another object of this invention to provide a flame or combustion zone which is substantially longer than that commonly obtained with open end burners and which can be adjusted to correspond to the length of a mineral deposit to be heated.

Other and related obiects will be apparent from the detailed description of my invention, and various advantages not specifically referred to herein will be apparent to those skilled in the art upon employment of the invention in practice.

l have now found that the foregoing objects and their attendant advantages can be realized by providing a continuous combustion zone extending the length of an elongated portion of a mineral deposit. The elongated combustion zone is achieved by use of an ignition propagating rod, eg. a ceramic, a sintered metal, or glass rod, surrounded by and concentrically placed within a burner tube.

My burner is described in more detail in reference to the drawing which forms a part of this application. In the drawing, FIGURE 1 shows the placement of one embodiment of my novel burner construction in a mineral deposit. Although FIGURE l illustrates a vertical disposition of my novel burner, it is apparent that a horizontal or inclined placement can also be employed if desired.

Referring now to FIGURE l, a heated mineral deposit B is shown located between unheated upper layer A and unheated lower layer C, said upper and lower layers typically comprising gravel, earth, stone, or an unheated portion of the mineral deposit. In accordance with this invention, a hole is bored through the earths surface into the mineral deposit. A metal casing 2 is positioned within the bore hole in the conventional manner. A single burner tube 4 is concentrically positioned within casing 2 and attached to the lo-wer end of conduit 3. A ceramic rod 6, which is of a length corresponding approximately to the depth of the mineral deposit to be heated, is supported and substantially concentrically positioned within burner tube 4. The gaseous combustible mixture to be burned can be of any suitable type, such as a mixture of natural gas and a combustion-sustaining medium such as air or any other oxygen-containing gas. Combustion mixture inlet 14, for the introduction of the combustible gas mixture to my burner system, receives fuel gas from fuel gas inlet 16 and combustion air from air inlet 18 and conducts the combustible gas mixture to burner tube 4 via the tubing string comprising conduit 3. Flue gas outlet 1li, for the removal of combustion products or ue gas, communicates with the annulus 4between burner tube 4 and casing 2.

The gas-air mixture from combustion mixture inlet 14 initially flows downwardly through conduit 3 and tube 4 and upwardly to ilue gas outlet 1t?. Combustion in this embodiment of the invention is then initiated by igniting the gas stream owing out of tube 10. The combuston zone is permitted to back up to burnertube 4 until a llame front exists at the lower end of burner tube 4. Ignition propagating ceramic rod 6 is positioned so that its lower end is within the combustion zone at the base of tube 4. Ceramic rod 6 then gradually heats up by conduction, and a red-hot ignition Vzone progresses up the length yof rod 6. t As this incandescent ignition zone moves upceramic rod 6, the combustion zone follows it until combustion exists Within burner tube 4 alongthe entire length of ceramic rod 6. Annular ring 12 is a flame arresting means placed within tube 4 above ceramic rod 6 to momentarily increase the combustible` -gas mixture ow rate thus preventing the combustion zone from moving above burner tubeV 4 through conduit 3 to combustion mixture inlet 14 or fuel gas inlet 16. Also, burner tube 4 can have a reduced diameter at its upper end to accomplish the same llame arresting purpose. Other ame arrestors, such as screens or grids, can also be employed. These ame arresting means can either be attached Vto burner tube 4 or be attached tofonly support member 8. Support member 8 is typically a wire line, but any suitable means can be used where it is desired that rod 6 be movable. Ceramic'rod 6, hanging on support member 8, is shown to be movable in a vertical direction, but ceramic rod 6 can be rigidly supported within tube 4 to simplify construction, particularly where the depth of the mineral formation is known.

During operation of the burner of my invention, flue gases are discharged fromthe lower open end of burner tube 4, reverse their direction of flow to pass upwardly through the annular zone formed between casing 2, burner tube 4, and conduit 3 and are removed throughV flue Agas conduit which is in open communication Vwith the in terior of casing 2. Heat is transmitted from the combuston zone by radiation to this upwardly owing stream ofl iiue gases and to the mineral deposits in zone B throughout the Ventire length of the burning zone along ignition propagating ceramic rod 6. Heat is also transmittedby convection fromvthe flue gases tothevmineral deposits.

By this method, a combustion zone with a substantiallyY uniform temperature is maintained along substantiallythe entire length of the heatedportion B of the mineral def posit. Although casing).` is shown to extend the length of the bore hole, it can be considerably shorter where the mineral matrix is suicientlyconsolidated so as not to fall into the hole. VWhen casing 2 does not extend the length of the bore hole, the heated portion of the mineral deposit can be directly heated by radiation from burner tube 4 with nointerve'ning casing 2. Suitable consolida-r tion can occur naturally or can be achieved by coking'the.

hydrocarbons in the deposit immediately adjacent the bore hole. This coking can be accomplished, for example, by introducing high temperature combustion gases into the hole.

' Other conventional ignition techniques to ignite gas Y burners in oil wells can also be employed in my invention.

Igntion is usually started at the bottom of burner tube 4, y

within the annulus between casing 2 and the inner tubing string, at the bottom of the bore hole, or at flue gas outlet 10. Among the suitable ignition techniques for starting combustion in burner tube 4 are the following: dynamite and percussion caps; electrically actuated heating coils and spark plugs which are positioned within the combustion zone and initiated by the supply of electrical energy from above ground; and chemical ignition techniques, e.g., a capsuleV of sodiumV or potassium is dropped into the well bore followed by injection of water and the sodium or potassium is then released, by mechanical breaking or dissolution of the capsule to react with the Water and release heat to ignite the gas. A description of these and otherV are suitable.Y The rod can assume any convenient geo-y metric form, can be solid or hollow, and can have any exterior surface nish, but preferably. the ignition propagating rod surface is rough.

Burner tube'4 can be constructed of any material which canwithstand the temperatures resulting in my combus-r tion zone. Typically, steel pipe or tubing is satisfactory With stainless steels being preferred, particularly those steels which are resistant to corrosion and embrittlement at high temperatures. Ceramic or other non-metallic materials can also be used for burner tube 4. v

In an example of the typical practice of this invention, apparatus substantially as shown in FIGURE 1 is used to supply heat toa 10'foot thick tar sand'deposit 50 feet below the earths surface. A vertical bore hole is drilled into the mineral deposit and a 5 inch vI.D. casing 2 is set therein. A burner tube 4 made of 3 inch O.D. stainless steel pipe having a 1A inch wall islowered into the hole and is concentrically positioned within casing 2. The burnertube 4 is 10 feet long and extends from the top to the bottom of the tar sand deposit. Within burnertube 4 is mounted a rough, irregular surfaced solid ignition propagating ceramic rod 6 yhaving aV diameter of about one inch. This rod 6 is'suspended from a wire line for easy removal or change of position. In' this embodiment, about 10,000 B.T.U. per hour'is distributed evenly over the 10 foot thickness of tar sand deposit. A gas-air mixture is introduced to the burner at combustible gas mixture inlet 14 and allowed to ll the void spaces until the combustible mixture exits through flue gas outlet'1'0. A ame is applied to the combustible mixture'issuing from outlet 10 which burns back to the lower end of burner tube 4; Ceramic rod 6 initially acts as a flame stabilizer and within a short time the lower end of rod 6 becomes incandescent and a hot zone moves up the rod. As the hot zone moves upward, the roughened surface of rod 6 provides local turbulence and additional ignition points for the combustible gas. This combustion process becomes self prop.

agating and the hot ignition propagating zone moves upward along the entire length of rod 6, providing a 10 foot long igniter and flame holder. The entire tar sand zone is thereby heated uniformly by radiation from burner tube 4. Without ceramic rod 6 iny place, a shortiiame, less than about 6 inches long, holdsat the end of burner tube 4 upon ignition. With a lower combustible gas mixture velocity than that used inv this example, Vthe short flame moves back to ame arrestor 12. With this arrangement, i.e., no Vceramic rod, heat distribution is non-uniform with a hot spot being located near the short flame zone.

This application is a division of my prior co-pending application Serial No. 828,106, led, July 20, 1959',v now issued as U.S. Patent No. 3,113,623.

Varous other changes and modifications of this invention are apparent from the description of this invention and further modifications will be obvious tothose skilled in the art. Such modifications and changes are intended to be included Vwithin the scope of this invention as de*- ned by the following claims. Y' 'Y I claim:

1. A burner in combination with'a well bore whichpenetrates an oil sand interval to be heated wherein said burner comprises an elongated metal tube open at its lower'end; a

a tubingstring extending into said well bore and connected Vtherein toV said burner;` i acombustible gas mixture supply conduitconuected to the uppertend of said tubing string; a conduit communicating with said well bore for the removal of ue gases therefrom; an ignition propagating rod concentric within said burner tube, said burner tube being of lesser diameter wthan'said well bore to form an annulus therebetween and said ignition propagating rod being of lesser diameter than said burner tube to form an annulus therebetween;

support means connected to said ignition propagating rod for concentrically positioning said ignition propagating rod within said burner tube; and

llame arresting means positioned in the combustible gas mixture flow path between said ignition propagating rod and said combustible gas mixture supply conduit.

2. An apparatus as defined in claim 1 including a casing within at least the upper extremity of said Well bore.

3. An apparatus as dened in claim 1 wherein said ignition propagating rod comprises a ceramic rod with a rough surface.

4. The combination with a well bore penetrating a subterranean oil sand interval which comprises:

a casing within said well bore;

a tubing string concentrically disposed within and spaced apart from said casing, said tubing string extending into said well bore to the upper level of said oil sand interval;

a conduit communicating with the upper end of the interior of said casing for the removal of flue gas therefrom;

an elongated burner tube concentrically disposed within and spaced apart from said well bore and connected to the lower end of said tubing string, said burner tube being open at its lower end and terminating at a lower level of said oil sand interval;

a combustible gas mixture supply conduit connected to the upper end of said tubing string;

an ignition propagating rod substantially concentrically disposed Within and spaced apart from said burner tube;

support means for positioning said ignition propagating rod Within said burner tube, said support means being connected to said ignition propagating rod; and

iiame arresting means positioned in the combustible gas mixture flow path between said ignition propagating rod and said combustible gas mixture supply conduit.

5. An apparatus as dened in claim 4 wherein said iirst tubing string extends into said well bore to at least the lower level of said oil sand interval.

6. An apparatus as defined in claim 4 wherein said ignition propagating rod comprises a ceramic rod with a rough surface.

7. A method of supplying heat substantially uniformly to an elongated region of subterranean oil-bearing mineral deposit which comprises:

boring a hole a substantial distance into said mineral deposit;

introducing a combustible gas mixture into a confined continuously elongated combustion zone located within and spaced apart from said hole; positioning an ignition propagating rod within said combustion zone so that one end of said ignition propagating rod extends into an initial combustion zone;

igniting said combustible mixture within said combustion Zone, said combustion Zone having a length substantially greater than the ilame of a jet of said combustible gas mixture and said combustion zone being substantially longitudinally and concentrically disposed Within said hole and extending the length of said elongated region, said combustible mixture being ignited initially at the end of said combustion zone nearest the bottom of said hole to form said initial combustion zone;

and withdrawing combustion gases from said combustion zone through said hole to the earths surface.

8. A method as defined in claim 7 wherein said combustible gas mixture comprises air and natural gas.

References Cited by the Examiner UNITED STATES PATENTS 2,396,868 3/46 McCollum 158-28 2,584,606 2/52 Merriam et al 166-11 2,890,755 6/59 Eurenius et al 166-59 2,981,250 4/61 Stewart 126-360 3,010,516 ll/6l Schleicher 166-11 X 3,113,623 12/63 Krueger 166-59 BENJAMIN HERSH, Primary Examiner. 

7. A METHOD OF SUPPOYING HEAT SUBSTANTIALLY UNIFORMLY TO AN ELONGATED REGION OF SUBTERRANEAN OIL-BEARING MINERAL DEPOSIT WHICH COMPRISES: BORING A HOLE A SUBSTANTIAL DISTANCE INTO SAID MINERAL DEPOSIT; INTRODUCING A COMBUSTIBLE GAS MIXTURE INTO A CONFINED CONTINUOUSLY ELONGATED COMBUSTION ZONE LOCATED WITHIN AND SPACED APART FROM SAID HOLE; POSITIONING AN IGNITION PROPAGATING ROD WITHIN SAID COMBUSTION ZONE SO THAT ONE END OF SAID IGNITION PROPAGATING ROD EXTENDS INTO AN INITIAL COMBUSTION ZONE; 